[Mesa-dev] [PATCH 20/29] i965/fs: Import image format metadata queries.

[Francisco Jerez]

Define some utility functions to query the bitfield layout of a given
image format and whether it satisfies a number of more or less
hardware-specific properties.

v2: Drop VEC4 suport.
---
 src/mesa/drivers/dri/i965/brw_fs_surface_builder.h | 147 +++++++++++++++++++++
 1 file changed, 147 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_surface_builder.h b/src/mesa/drivers/dri/i965/brw_fs_surface_builder.h
index 264314b..e3cceeb 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_surface_builder.h
+++ b/src/mesa/drivers/dri/i965/brw_fs_surface_builder.h
@@ -65,5 +65,152 @@ namespace brw {
                         unsigned dims, unsigned rsize, unsigned op,
                         brw_predicate pred = BRW_PREDICATE_NONE);
    }
+
+   namespace image_format_info {
+      /**
+       * Simple 4-tuple of scalars used to pass around per-color component
+       * values.
+       */
+      struct color_u {
+         color_u(unsigned x = 0) : r(x), g(x), b(x), a(x)
+         {
+         }
+
+         color_u(unsigned r, unsigned g, unsigned b, unsigned a) :
+            r(r), g(g), b(b), a(a)
+         {
+         }
+
+         unsigned
+         operator[](unsigned i) const
+         {
+            const unsigned xs[] = { r, g, b, a };
+            return xs[i];
+         }
+
+         unsigned r, g, b, a;
+      };
+
+      /**
+       * Return the per-channel bitfield widths for a given image format.
+       */
+      inline color_u
+      get_bit_widths(mesa_format format)
+      {
+         return color_u(_mesa_get_format_bits(format, GL_RED_BITS),
+                        _mesa_get_format_bits(format, GL_GREEN_BITS),
+                        _mesa_get_format_bits(format, GL_BLUE_BITS),
+                        _mesa_get_format_bits(format, GL_ALPHA_BITS));
+      }
+
+      /**
+       * Return the per-channel bitfield shifts for a given image format.
+       */
+      inline color_u
+      get_bit_shifts(mesa_format format)
+      {
+         const color_u widths = get_bit_widths(format);
+         return color_u(0, widths.r, widths.r + widths.g,
+                        widths.r + widths.g + widths.b);
+      }
+
+      /**
+       * Return true if all present components have the same bit width.
+       */
+      inline bool
+      is_homogeneous(mesa_format format)
+      {
+         const color_u widths = get_bit_widths(format);
+         return ((widths.g == 0 || widths.g == widths.r) &&
+                 (widths.b == 0 || widths.b == widths.r) &&
+                 (widths.a == 0 || widths.a == widths.r));
+      }
+
+      /**
+       * Return true if the format conversion boils down to a trivial copy.
+       */
+      inline bool
+      is_conversion_trivial(const brw_device_info *devinfo, mesa_format format)
+      {
+         return (get_bit_widths(format).r == 32 && is_homogeneous(format)) ||
+                 format == brw_lower_mesa_image_format(devinfo, format);
+      }
+
+      /**
+       * Return true if the hardware natively supports some format with
+       * compatible bitfield layout, but possibly different data types.
+       */
+      inline bool
+      has_supported_bit_layout(const brw_device_info *devinfo,
+                               mesa_format format)
+      {
+         const color_u widths = get_bit_widths(format);
+         const color_u lower_widths = get_bit_widths(
+            brw_lower_mesa_image_format(devinfo, format));
+
+         return (widths.r == lower_widths.r &&
+                 widths.g == lower_widths.g &&
+                 widths.b == lower_widths.b &&
+                 widths.a == lower_widths.a);
+      }
+
+      /**
+       * Return true if we are required to spread individual components over
+       * several components of the format used by the hardware (RG32 and
+       * friends implemented as RGBA16UI).
+       */
+      inline bool
+      has_split_bit_layout(const brw_device_info *devinfo, mesa_format format)
+      {
+         const mesa_format lower_format =
+            brw_lower_mesa_image_format(devinfo, format);
+
+         return (_mesa_format_num_components(format) <
+                 _mesa_format_num_components(lower_format));
+      }
+
+      /**
+       * Return true unless we have to fall back to untyped surface access.
+       * Fail!
+       */
+      inline bool
+      has_matching_typed_format(const brw_device_info *devinfo,
+                                mesa_format format)
+      {
+         return (_mesa_get_format_bytes(format) <= 4 ||
+                 (_mesa_get_format_bytes(format) <= 8 &&
+                  (devinfo->gen >= 8 || devinfo->is_haswell)));
+      }
+
+      /**
+       * Return true if the hardware returns garbage in the unused high bits
+       * of each component.  This may happen on IVB because we rely on the
+       * undocumented behavior that typed reads from surfaces of the
+       * unsupported R8 and R16 formats return useful data in their least
+       * significant bits.
+       */
+      inline bool
+      has_undefined_high_bits(const brw_device_info *devinfo,
+                              mesa_format format)
+      {
+         const mesa_format lower_format =
+            brw_lower_mesa_image_format(devinfo, format);
+
+         return (devinfo->gen == 7 && !devinfo->is_haswell &&
+                 (lower_format == MESA_FORMAT_R_UINT16 ||
+                  lower_format == MESA_FORMAT_R_UINT8));
+      }
+
+      /**
+       * Return true if the format represents values as signed integers
+       * requiring sign extension when unpacking.
+       */
+      inline bool
+      needs_sign_extension(mesa_format format)
+      {
+         return (_mesa_get_format_datatype(format) == GL_SIGNED_NORMALIZED ||
+                 _mesa_get_format_datatype(format) == GL_INT);
+      }
+   }
 }
 #endif
-- 
2.3.5